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Definitions

• the invention relates to finely divided lead zirconate titanates (PZT), zirconium titanium hydrates (ZTH) and zirconium titanates as precursors for lead zirconate titanates, a process for their preparation by reaction of titanium dioxide particles with a zirconium compound or a lead and zirconium compound. Furthermore, the invention relates to a microelectronic device containing a lead zirconate titanate.
• PZT lead zirconate titanates
• ZTH zirconium titanium hydrates
• zirconium titanates as precursors for lead zirconate titanates
• PZT Lead zirconate titanate
• PZT powder is usually made from the raw materials lead oxide, zirconia and titanium dioxide.
• the composition can be given by formula as Pb (Zr x Ti) __ x ) O3 with 0 ⁇ x ⁇ l.
• doping elements are usually included (generally about 1-3% in total). Typical dopants are lanthanum, neodymium, strontium, potassium, iron, gadolinium and niobium.
• PZT ceramics Starting materials for such PZT ceramics are calcined PZT mixed oxide powders, which are pressed into moldings or processed into coatings or films and then sintered to form a ceramic.
• Lead zirconate titanate oxide powders can be prepared by synthetic methods that proceed via solid-state reactions (mixed oxide method), and by wet-chemical methods (eg sol-gel process, coprecipitation method or spray reaction method).
• the sinterability or sintering temperature of the powder is not only dependent on the composition, but also on the history of the respective material, ie the degree of activation, the particle size and particle size distribution, the particle shape and the density of the green body (ie after shaping and before sintering ).
• the calcination of the starting powders is carried out in the powders prepared by the conventional methods at relatively high reaction temperatures in order to obtain almost phase-pure PZT mixed crystals.
• the high calcination temperatures reduce the sintering activity of the PZT mixed crystals.
• reaction temperatures are when using oxidic reactants at about 800-900 0 C, using reactants, which are prepared by the sol-gel method in the range of 450 to 700 0 C.
• the corresponding sintering temperatures are about 1100-1250 0 C (oxidic reactants) or ⁇ 1000 ° C (sol-gel reactants).
• the multilayer piezoactuators consist of stacked ferroelectric ceramic layers with a layer thickness of about 10 to 200 .mu.m. Between each ceramic layer is an approximately 1-3 microns thick metal electrode, which serves to control the actuator. These multilayer piezoelectric actuators ideally have relatively high Curie temperatures, so that applications at higher temperatures are possible. In addition, they are characterized by high piezoelectric and electromechanical characteristics and fatigue resistance.
• the object of the present invention is to prepare finely divided, sinter-active, readily processable and economically producible lead zirconate titanates, zirconium titanates and zirconium titanates as precursors for lead zirconate titanates, from which PZT ceramics can be produced which densify well at low sintering temperatures.
• a process for their preparation using simple titanium-containing substrates is to be provided, wherein a simple and economical production method is used.
• the object is achieved on the one hand by processes for the preparation of zirconium titanates, zirconium titanium hydrates or lead zirconate titanates by reacting finely divided titanium dioxide particles having a specific surface area of more than 50 m 2 / g with a zirconium compound or a lead and zirconium compound.
• the object is further achieved by the provision of zirconium titanium hydrates, zirconium titanates and lead zirconate titanates which can be prepared by the processes according to the invention.
• the invention additionally encompasses the provision of a microelectronic component, in particular a PZT multilayer actuator, produced with the aid of a lead zirconate titanate material according to the invention.
• the titanium dioxide particles are the titanium dioxide particles.
• the finely divided titanium dioxide particles used according to the invention have a BET surface area of more than 50 m 2 / g, preferably less than 450 m 2 / g, particularly preferably 200 to 380 m 2 / g, particularly preferably 250 to 350 m 2 / g.
• the BET surface area is determined according to DIN ISO 9277 using N 2 at 77 K on a degassed at 140 0 C for 1 hour and dried sample of titanium dioxide particles. The evaluation is carried out by multi-point determination (10-point determination).
• the titanium dioxide particles used in the present invention are regularly titania hydrate particles, i. the particles contain chemisorbed water and optionally SO4 and / or further inorganic and / or organic constituents.
• the titanium dioxide particles preferably contain from 0.4 to 25% by weight, more preferably from 2 to 10% by weight, of water.
• the SO 4 content of the titanium dioxide particles is preferably less than 1% by weight, more preferably between 0.01 to 0.4 wt .-%, particularly preferably between 0.01 to 0.08 wt .-%, based on TiC> 2.
• the determination of the H2O content of the titanium dioxide particles can be carried out according to the following equation:
• H 2 O content (%) loss on ignition (%) - H 2 SO 4 content (%)
• the loss on ignition is the weight loss of a sample dried according to ISO 787 Part 2 after annealing for 1 hour at a temperature of 1000 ° C.
• the S ⁇ 4 content is determined on the basis of the analytical determination of the sulfur content of the sample dried according to ISO 787 Part 2.
• the sulfur content is determined by combustion and gas chromatographic detection of the combustion gases by means of thermal conductivity detection (WLD).
• the H 2 O content of the titanium dioxide particles can also be equated with the loss on ignition after one hour of annealing of the sample dried according to ISO 787 Part 2 at 500 ° C.
• H2 ⁇ content of the titanium dioxide particles can be carried out, for example, by gas chromatographic analysis of the volatile constituents which, after one hour of annealing, occur at a temperature of 1000 ° C. of a sample dried according to ISO 787 part 2.
• the halide content of the titanium dioxide particles used according to the invention is preferably less than 1000 ppm, more preferably less than 500 ppm, particularly preferably less than 50 ppm, based on TiO 2 .
• the chloride content of the particles is preferably less than 200 ppm, in particular less than 100 ppm, particularly preferably less than 20 ppm, based on TiO 2 •
• the content of niobium of the titanium dioxide particles may be 10 to 2000 ppm, preferably 30 to 500 ppm, more preferably 50 to 300 ppm, in particular 50 to 120 ppm, based on TiO 2.
• the content of sodium and / or potassium of the titanium dioxide particles used according to the invention is preferably less than 200 ppm, more preferably less than 50 ppm, based on TiO 2.
• the content of iron of the titanium dioxide particles used according to the invention is preferably less than 100 ppm, more preferably less than 10 ppm, based on TiC> 2.
• the titanium oxide hydrate particles used according to the invention can be obtained by hydrolysis of inorganic or organic titanium compounds. Depending on the titanium compound and the reaction conditions, different properties of the resulting titanium dioxides result.
• the titanium oxide hydrate particles used according to the invention can be produced in good quality and at low cost.
• the titanium oxide hydrate particles may also be prepared from titanium tetrachloride or titanium alkoxide.
• titanium oxide hydrate which is obtained by hydrolysis of titanyl sulfate solution
• This anatase structure can be identified as a microcrystalline material due to the broad reflections of the X-ray diffraction pattern (see Fig. 1).
• the particles used according to the invention therefore preferably contain less than 10% by weight, more preferably less than 1% by weight, of rutile, based on TiC> 2.
• Particular preference is given to titanium dioxide particles which clearly show an anatase structure in the X-ray diffractogram.
• the titanium oxide hydrate particles can be obtained, for example, by hydrolysis of a sulfuric acid-containing titanyl sulfate solution.
• a sulfuric acid suspension of titanium oxide hydrate is obtained during the hydrolysis, which may still contain undesired impurities, in particular heavy metals.
• one or more purification steps are carried out to rid the titanium oxide hydrate of unwanted impurities.
• Titanium oxide hydrate particles are preferably used which are formed by hydrolysis of titanyl sulfate, which is obtained in the titanium dioxide production process by the sulphate process. This process is described, for example, in Industrial Inorganic Pigments, 3rd Edition, Editors Gunter Buxbaum, Gerhard Pfäff, Wiley-VCH, 2005.
• the titanium oxide hydrate obtained after the hydrolysis is freed of adhering impurities by being filtered and washed and, if appropriate, additionally subjected to the process step of the so-called bleaching, a chemical treatment with reducing agents for the elimination of trivalent iron.
• the large-scale production of titanium oxide hydrate based on the sulfate process for titanium dioxide production also has the advantage of a constant product quality and constant availability.
• a titanyl sulfate solution can be prepared, for example, by hydrolysis of high-purity TiCl 4 or titanium esters and dissolving the resulting precipitate with sulfuric acid.
• the production of a high-purity titanium oxide hydrate therefrom can be carried out either analogously to conventional large-scale industrial processes or with specific deviations.
• the adhered sulfuric acid is removed by reaction with a base (e.g., NaOH, KOH, NH 3) followed by washing out the resulting sulfate.
• a base e.g., NaOH, KOH, NH 3
• subsequent elimination of the cations introduced by the reaction with the base can be accomplished by reaction with thermally readily decomposable acids (e.g., carboxylic acids or nitric acid) followed by washing.
• titania hydrate obtained from titanyl sulfate are its high purity with respect to iron and other heavy metals, as well as its extremely low levels of chloride.
• the titanium dioxide particles may be treated by a calcining or annealing step to selectively modify the particle size and reactivity.
• the conversion of microcrystalline titania hydrate into slightly larger anatase crystallites may be advantageous.
• the calcination or annealing step should be carried out so that the particular properties of the titanium oxide hydrate are not lost, ie the proportion of chemisorbed water (for example in the form of hydroxyl groups) should not be less than 0.4% by weight, preferably 2.0 wt .-%, to the most reactive surface of the To maintain titanium oxide hydrate.
• titanium oxide hydrate calcined at high temperatures the reactivity decreases markedly, whereas the titanium oxide hydrate turns into macrocrystalline TiC> 2 with a crystal size greater than 100 nm in the anatase or rutile modification with a content of chemisorbed water of less than 0.4% by weight. % converted.
• coarser titanium-containing particles induce the formation of a coarser zirconium titanate or lead zirconate titanate.
• titanium oxide hydrate particles which after one hour annealing of a sample pre-dried according to ISO 787 part 2 at a temperature of 1000 ° C. have an ignition loss of more than 2% by weight, preferably more than 6% by weight and / or after one hour Annealing at 500 ° C. has an ignition loss of more than 0.8% by weight, preferably more than 1.2% by weight.
• the described method steps according to the invention which provide a technically and economically improved production process for forming nanoparticulate titanium oxide hydrate-containing materials compared with conventional gas phase processes, give primary particles of the titanium oxide hydrate having an average particle size of 3 to 15 nm, preferably 4 to 8 nm ,
• the primary particles are small, approximately spherical, microcrystalline particles with a lattice-disordered anatase structure.
• the particle size can be calculated by calculation from the BET surface assuming a monomodal Grain size distribution of spherical particles can be determined.
• the relationship between the mean particle size d and the specific surface area SBET (determined by BET) is assuming a monomodal
• the titanium dioxide particles used in accordance with the invention in combination with zirconium compounds, in particular with finely divided hydroxidal zirconium compounds have significant advantages over conventional titanium dioxide, for example zirconium titanates or lead zirconate titanates.
• commercially available technical titanium dioxides with mean particle sizes of about 200 nm.
• the small particle size of titanium oxide hydrate and the high reactivity in the reaction with a zirconium compound, in particular with finely divided hydrous zirconium compound or a lead compound and a finely divided hydroxidal zirconium compound, particularly finely divided and sintered zirconium titanates or lead zirconate titanates are obtained.
• the low chloride content of the titanium oxide hydrate particles according to the invention has a positive effect on the properties of the zirconium titanates or lead zirconate titanates.
• the low content of chloride and metallic Trace elements has a favorable effect on the properties of the zirconium titanates or lead zirconate titanates prepared from titanium oxide hydrate. Especially at low reaction temperatures to zirconium titanate or lead zirconate titanate, the presence of halides is disturbing.
• the titanium dioxide particles are reacted according to the invention with one or more zirconium compounds or lead and zirconium compounds. These are usually oxides or salts of lead or zirconium.
• the salts include acetates, carbonates, oxalates, hydroxides, oxide chlorides, oxide sulfates, nitrates, halides such as chlorides, as well as organic compounds such as alkoxides and salts of carboxylic acids.
• zirconium compounds particularly preferably zirconium oxide (ZrO 2), zirconyl chloride (ZrOCl 2) and zirconyl sulfate (ZrOSO ⁇ used.
• the lead compounds are lead oxide (PbO), lead nitrate (Pb (NO 3) 2), lead acetate (Pb (OAc) 2) and other easily decomposable lead compounds or mixtures thereof are particularly preferred.
• the decomposition temperatures may e.g. in combined thermogravimetry (TG) and differential thermal analysis (DTA) apparatus.
• TG thermogravimetry
• DTA differential thermal analysis
• zirconium compounds which are used in the form of a precipitated product having a BET surface area of more than 20 m.sup.2 / g, preferably more than 50 m.sup.2 / g, particularly preferably more than 100 m.sup.2 / g. by neutralization of an aqueous Zirconium salt solution is obtained.
• the precipitate is precipitated on the titanium dioxide particles.
• the determination of the BET surface area is carried out analogous to that of the titanium dioxide particles according to DIN ISO 9277 by means of N 2 at 77 K in a degassed at 140 0 C for 1 hour, dried sample of the precipitate.
• Such a precipitate may contain one or more of the compounds zirconium hydroxide, zirconium oxyhydroxide or zirconium oxide.
• titanium dioxide particles characterized above are used according to the invention in a process for the preparation of zirconium titanates or lead zirconate titanates with the abovementioned zirconium compounds or lead and zirconium compounds.
• zirconium titanates the titanium dioxide particles and zirconium oxide or zirconium hydroxide can be ground together dry and then calcined or partially calcined.
• lead zirconate titanates can be prepared by co-grinding titanium dioxide particles, zirconium oxide or zirconium hydroxide and a lead compound, e.g. Lead oxide, lead nitrate or lead acetate. Again, this may be followed by calcination or Generalkalzinleiter.
• the titanium dioxide particles can also be reacted with a water-soluble zirconium compound (eg zirconyl chloride or zirconyl sulfate), wherein the particles in the already prepared Zr-containing or Zr and Pb-containing solution or together with the Zr-SaIz or Zr and Pb -SaIz be suspended in water.
• a water-soluble zirconium compound eg zirconyl chloride or zirconyl sulfate
• the reaction takes place by the neutralization of the suspension, for example by adding ammonia or sodium hydroxide, the zirconium compound precipitating in the form of oxidic and / or hydroxide compounds.
• the neutralization is carried out to a pH of 7 to 8.
• the mixture obtained in this way can be separated by filtration and optionally subsequently washed and dried, so that a powdery material consisting of titanium dioxide and precipitated oxides and / or hydroxides of zirconium or consisting of titanium dioxide and precipitated oxides and / or hydroxides of zirconium and of the lead is present.
• the obtained mixture can either be wet-blasted before drying, preferably bead-blasted or dry-dried after drying, whereby the calcining or sintering activity can be further improved even further.
• the product low in chloride or sulfur is dried.
• the drying may, if necessary, a calcination or Generalkalzinleiter at a maximum temperature of 650 0 C, preferably at most connect 600 0 C.
• the calcination or Generalkalzin mich mich takes place at a temperature below 500 0 C, more preferably below 400 0 C. If the reaction in the presence of a lead compound and / or other doping compounds such as lanthanum or niobium compounds by, it is obtained according to Calcination according to doped or non-doped lead zirconate titanate.
• the preparation of the lead zirconate titanates can also be carried out in two stages, with the zirconium titanates in a first stage in one of the ways described above are prepared and then ground in a second stage with a lead compound in a liquid medium. Also in this case, the drying is followed by calcination at a temperature of at most 650 ° C., preferably at most 600 ° C.
• the zirconium titanate or lead zirconate titanate can also be obtained directly under hydrothermal conditions by reacting the titanium dioxide particles with a zirconium compound or lead and zirconium compound.
• the exact desired Zr / Ti ratio can be adjusted by mixing two homogeneous zirconium titanium hydrate reactants with different Zr / Ti ratios, with the lead compound and doping components also being added to this mixture.
• it is also possible to set the exact desired Pb / Zr / Ti ratio by mixing two homogeneous zirconium titanium hydride starting materials with different Zr / Ti ratio and a third starting material which additionally contains the lead compound in addition to zirconium titanium hydrate and also adding the doping components to this mixture become.
• the calcination of the titanium dioxide particles with the zirconium compound or lead and zirconium compound is preferably not isothermal, but at approximately constant conversion rate to zirconium titanate or lead zirconate titanate (SCRT method described for BaTiC> 3 in Gotor et al., J.Europ.Cer. Soc.23 (2003), 505-513).
• the zirconium titanate or lead zirconate titanate can be further comminuted by milling, eg bead milling.
• the further processing after the calcination can also be done without any intervening grinding step.
• sintering preferably takes place at a temperature of at most 1050 ° C., more preferably below 950 ° C.
• Calcination and sintering can also take place in a single step in the form of "reaction sintering".
• a relative density of at least 97%, particularly preferably at least 98.5%, is preferably achieved.
• the pulverulent lead zirconate titanates or zirconium titanates according to the invention are finely divided, poorly agglomerated, reactive and have a very homogeneous distribution of the individual elements.
• the proportions of lead compound / zirconium compound / titanium dioxide particles (and optionally further doping elements) are set by exact weighing.
• the molar ratio Pb: Zr: Ti can be adapted according to the specific application requirement of the lead zirconate titanate or zirconium titanate.
• the process step of the grinding after calcination can either be completely or partially saved due to the low calcination temperatures and the low agglomeration of the resulting PZT particles. This represents a significant cost advantage over the conventional procedure.
• the sintering of the lead zirconate titanates according to the invention occurs, as compared to conventional powders, a compression already at lower temperatures. Ceramics made from these materials can thereby be produced at lower sintering temperatures. Alternatively, by virtue of the improved compaction behavior compared with a conventional powder, ceramics with higher densities can be produced at the same sintering temperatures.
• the microstructures of the ceramics from the lead zirconate titanates according to the invention are very fine-grained.
• the small grain sizes are advantageous for the production of components with very small dimensions. Since, given a small particle size, a given volume contains a larger number of grains with different crystallographic orientations, the local inhomogeneities due to the anisotropic properties of the materials are reduced. With small particle sizes, the coercive field strengths are high and the field-induced strains and other electro-mechanical properties are low.
• grain growth can be achieved by means of suitable doping. By suitable combination of donor and acceptor doping, grain size and electromechanical properties will be adjusted at a given sintering temperature. Electrical and electromechanical properties can thereby be increased, the coercive field strengths reduced. Decisive for the particle sizes is the donor excess. Preparations of titanium oxide hydrate particles and zirconium compounds or zirconium and lead compounds
• the invention also provides compositions containing titanium oxide hydrate particles having a BET surface area of more than 50 m 2 / g and a compound, preferably hydroxidic, obtained from a water-soluble zirconium compound or a water-soluble lead and zirconium compound.
• such preparations are in dried form. These are preferably pulverulent preparations.
• a water-soluble zirconium compound or a water-soluble lead and zirconium compound or an aqueous solution of a zirconium salt or a lead and zirconium salt is added to titanium oxide hydrate or an aqueous suspension of titanium oxide hydrate and this suspension is neutralized, filtered and the filter cake obtained is dried and dried ,
• a titanium oxide hydrate is obtained, on the surface of which the zirconium compound or the lead and zirconium compound are uniformly distributed.
• the titanium oxide hydrate thus coated and / or intimately mixed with the zirconium compound or lead and zirconium compound can subsequently be calcined.
• the lead or zirconium compounds are preferably oxidic and / or hydroxidic compounds.
• the titanium / zirconium ratio lies (Molar ratio) preferably between 0.25 and 4, particularly preferably between 0.66 and 1.00 and in particular between 0.75 and 0.9.
• the molar ratio [Zr] / [Ti] is preferably 0.25 to 4, more preferably 1.00 to 1.50, and the molar ratio [Pb] / ([ Zr] + [Ti]) is preferably 0.95 to 1.05, more preferably 0.95 to 1.0.
• doping compounds e.g. Nd, Sr, La, Nb, Ca, Na, K, Cu, Ni or Fe salts or the corresponding oxides are added.
• zirconium titanium hydrate ZTH
• zirconium titanate or lead zirconate titanate
• the invention provides a preparation of zirconium titanium hydrate (ZTH) obtainable according to the process of the invention from titanium oxide hydrate particles having a BET surface area greater than 50 m 2 / g and a zirconium compound, the molar ratio of zirconium and titanium being between 0.25 and 4 lies.
• ZTH zirconium titanium hydrate
• a pulverulent preparation of zirconium titanium hydrate is preferably provided, wherein the zirconium compound, preferably as an oxidic and / or hydroxide compound, is deposited on the titanium oxide hydrate particles and the mixture is then dried.
• the zirconium compound preferably as an oxidic and / or hydroxide compound
• the BET surface area of this powder preparation from Zirkontitanhydrat (ZTH) is preferably more than 50 m ⁇ / g, preferably more than 100 m ⁇ / g, more preferably more than 150 m 2 / g.
• the chloride content of this powdered preparation of zirconium titanium hydrate (ZTH) is preferably less than 100 ppm, more preferably less than 30 ppm.
• the invention also provides lead zirconate titanates or zirconium titanates as precursors for lead zirconate titanates obtainable from zirconium titanium hydrate (ZTH).
• the lead zirconate titanate according to the invention can be described by the compositional formula Pb (Zr x Ti] __ x) O3 where 0 ⁇ x ⁇ l, preferably 0.4 ⁇ x ⁇ 0.8 describe.
• the chloride content of the zirconium titanates or lead zirconate titanates is preferably less than 100 ppm, particularly preferably less than 30 ppm and in particular less than 10 ppm.
• the niobium content of zirconium titanium hydrates (ZTH) or zirconium titanates is preferably from 10 to 300 ppm, particularly preferably from 15 to 100 ppm and in particular from 20 to 50 ppm.
• the niobium content of the lead zirconate titanates is preferably 1 to 300 ppm, particularly preferably 10 to 300 ppm, in particular 5 to 15 ppm.
• zirconium titanium hydrates (ZTH), zirconium titanates or lead zirconate titanates according to the invention preferably contain less than 1% of sulfate, especially preferably less than 500 ppm and in particular less than 200 ppm.
• zirconium titanium hydrates (ZTH), zirconium titanates or lead zirconate titanates according to the invention preferably contain less than 200 ppm, more preferably less than 50 ppm, sodium or potassium.
• zirconium titanium hydrates (ZTH), zirconium titanates or lead zirconate titanates according to the invention preferably contain less than 20 ppm iron, preferably less than 5 ppm.
• phase purity of the product according to the invention can be determined by means of powder X-ray diffractometry (XRD).
• the sintering of the materials produced on the basis of the powders according to the invention into ceramics with sufficient densities can be carried out at a relatively low temperature.
• the densities achievable at a given sintering temperature can be further increased by using suitable additives.
• titanium dioxide particles according to the invention it is particularly advantageous to grind the titanium dioxide particles according to the invention either alone or together with the zirconium compounds used.
• a wet grinding is used for this purpose, for example a bead mill.
• the lead compound and / or further doping constituents may also be present.
• the lead zirconate titanates according to the invention can be used for producing a microelectronic component, for example a multilayer piezoelectric actuator. Due to the fineness of the obtained lead zirconate titanates, it is possible to realize particularly thin layers and therefore particularly small component dimensions. In particular, the use in ceramic multilayer piezoelectric actuators comes into consideration, due to the fineness of the lead zirconate according to the invention particularly thin layers with a layer thickness of preferably less than 100 .mu.m, more preferably less than 80-50 microns, especially less than 20 microns, and most preferably less than 10 microns, can be obtained.
• the high sintering activity or low sintering temperature of the lead zirconate titanates according to the invention enables the use of low-melting and low-cost electrode material.
• electrodes made of an Ag / Pd alloy with a higher Ag content than usual can be used.
• Such components can be produced, for example, by preparing a slip from the lead zirconate titanate, if appropriate together with organic additives, and drawing it out to thin films by various methods (for example, film-doctoring method). Corresponding components may also be pressed after the lead zirconate titanate has been added with a pressing aid (e.g., organic binder) to a green body which is burned out prior to the sintering process.
• a pressing aid e.g., organic binder
• finely divided lead zirconate titanates according to the invention in a mixture with conventional coarser lead zirconate titanates. That way to specifically influence the microstructure of the resulting ceramic.
• a microstructure which is characterized by a specific mixture of small and large grains, can be adjusted, which in turn allows a specific property profile.
• the grain size of the sintered ceramic in a targeted manner by suitable doping; In particular, by doping the grain size of the sintered ceramic can be selectively increased at a given sintering temperature.
• 300 mg / g corresponds to a crystallite size of 6 nm, analytical data based on TiC> 2: 700 ppm S, 89 ppm Nb, 12 ppm Fe) suspended in water and treated with an aqueous zirconyl chloride solution.
• the proportions of the reactants are chosen so that the molar ratio of Zr to Ti is 0.525 to 0.475.
• aqueous suspension of titanium oxide hydrate obtained in the production of titanium dioxide by the sulfate process after the process step of bleaching (microcrystalline anatase, about 7% by weight of sulfate based on TiO 2, BET: about 300 m 2 / g, corresponds to a crystallite size of 6 nm) zirconyl chloride solution is added.
• the proportions of the reactants are chosen so that the molar ratio of Zr to Ti is 0.525 to 0.475.
• Titanoxidhydratp noticed.
• the suspension is filtered, washed and dried the filter cake obtained.
• aqueous suspension of titanium oxide hydrate which is obtained in the production of titanium dioxide by the sulfate process after the process step of bleaching, (microcrystalline anatase, about 7 wt .-% sulfate based on TiO 2 , BET: about 300 m 2 / g , corresponds to a crystallite size of 6 nm) zirconyl chloride solution and ammonia solution are added simultaneously, whereby the dissolved zirconium is precipitated on the Titanoxidhydratpelle.
• the suspension is maintained in a pH range of 6-8 and adjusted to pH 7.8 with ammonia after adding the entire amount of zirconyl chloride solution.
• the proportions of the reactants are such that the molar ratio of Zr to Ti is 0.544 to 0.456.
• the suspension is filtered, washed and the filter cake obtained spray-dried.
• the dried zirconium titanium hydrate (ZTH) has the following parameters:
• the suspension is filtered, washed and the filter cake obtained again with water to a suspension (about 10% solids content) vermaischt.
• This suspension is ground in a bead mill (LME 4 from Netzsch) with ZrC> 2 grinding balls (0.4-0.7 mm) with a residence time of 3 min per passage in two passages (total residence time 6 min, energy input approx. 200 kWh / t solid, temperature increase during grinding by about 19 K).
• the resulting ground suspension is then spray dried.
• the dried zirconium titanium hydrate (ZTH) has the following parameters:
• a powder mixture ground and dried in an attritor consisting of PbO (Alfa AESAR, purity 99.99%), Zr / Ti hydrate (from Example Ic) and La2Ü3 (doping element, Alfa AESAR, purity 99, 9%) corresponding to later stoichiometric composition Pbg 97 Lag 02 (% r 0 525 ⁇ i ⁇ 475) 03, is sieved and then calcined at a temperature of T 400 0 C in an oven in air for 2 h in PbO saturated alumina crucibles. In this case, the moisture content is taken into account when weighing the Zr / Ti hydrate powder.
• PZT lead zirconate titanate
• a powder mixture ground and dried in an attritor consisting of PbO (Alfa AESAR, purity 99.99%), ZrO 2 (Tosoh), TiO 2 (TR-HP-2 from Kerr-McGee) and La 2 ⁇ 3 (doping element, Fa. Alfa AESAR purity 99, 9%) corresponding to the later stoichiometric composition Pbg 97 La 0, 02 (ZrQ t 5 2 5Tig t 475) O3 (see Example 2) is added in an air oven for 2 hours 850 0 C calcined.
• the powder is ground after calcination in isopropanol, dried, sieved and further processed to green bodies by uniaxial and cold isostatic pressing. Subsequently, the green bodies are sintered at 950-1050 0 C for 6 hours in air.
• the samples are in a closed Al 2 O 3 crucible (procedure see example 3).
• the preparation of ceramic specimens is carried out until calcination as in Example 3, but then the powder calcined at 400 0 C without further grinding or screening immediately processed into green bodies by uniaxial and cold isostatic pressing and then sintered.
• a density of 97% of the theoretical density is obtained.
• a density of 95% of the theoretical density is obtained.
• a powder mixture ground and dried in an attritor, consisting of PbO, Zr / Ti hydrate (from Example Ib) and La2Ü3 (doping element) is processed by uniaxial and cold isostatic pressing directly into green bodies and then sintered. This means that sintering and calcining take place in one process step (reaction sintering). The relative densities of the reaction sintered samples are 92%.
• the dried Ti-Zr-hydrate obtained from Example Id is calcined in a muffle furnace for 2 hours at 125O 0 C Where a crystalline zirconium titanate is obtained.
• an aqueous suspension of titanium oxide hydrate (9% by weight of volatile constituents, anatase, BET: 271 m 2 / g, corresponds to a crystallite size of 6 ni; analytical data based on TiO 2: 700 ppm S, ⁇ 20 ppm Cl, 310 ppm Nb, 10 ppm Fe) is added an aqueous lead acetate solution and then an aqueous zirconyl sulfate solution.
• the proportions of the reactants are chosen that the lead zirconate titanates produced therefrom have a composition corresponding to the formula Pb 0, 98 (Zr 0, 0 54Ti, 46) O 3.
• Example 8 The material obtained from Example 8 is calcined for 30 minutes at a temperature of 500 0 C. In the X-ray diffractogram PbTiO 3 and PbZrO 3 are detected; the anatase reflexes present before calcination have completely disappeared.
• Powdered titanium oxide hydrate (composition as in Example 8) is mixed with finely divided zirconium oxide and lead oxide and ground.
• the proportions of the reactants are chosen so that the lead zirconate titanates which can be prepared therefrom have a composition in accordance with the formula Pbg 98 (ZrQ 5 O 4 O 46) O 3 .
• the resulting powder mixture converts to lead zirconate titanate at lower temperatures than an analogous powder mixture using a titania component having a particle size of 200 nm instead of the titania hydrate.
• Example 11 comparative example
• an aqueous suspension of titanium dioxide in the rutile modification with a particle size of 200 nm and a BET surface area of 6 m 2 / g an aqueous lead acetate solution and then an aqueous zirconyl sulfate solution is added.
• the proportions of the reactants are chosen so that the lead zirconium titanates prepared therefrom have a composition in accordance with the formula PbQ, 98 ( Zr 0, 54 T: > -0.46 ⁇ 3 by addition of ammonia up to a pH of 7 , The dissolved compounds are precipitated onto the titanium dioxide, the suspension is filtered, washed and the resulting filter cake is dried, and the resulting material is calcined for 30 minutes at a temperature of 500 ° C.
• the titanium dioxide has only partially reacted at this temperature; In the X-ray diffraction pattern, significant amounts of rutile are detected in addition to various other phases.

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